[GAMEPLAY] While playing as Sylas against Teemo I encountered a large ult bug

I stole Teemo's ult and was holding onto hit while I hit level 11. I leveled up my Ultimate while I still had the Teemo shrooms, and afterwards I was left with a 36 minute cool down on my ultimate. I think about 3 minutes or so later after a teamfight the ultimate cooldown ended up reverting back to the normal shroom cool down, nontheless I was ult-less for about 5-7 minutes.